The top 5 biomarkers all showed great potential in identifying culture-negative episodes that were characterized by relatively low total cell counts, an increased proportion of CD14+ monocytes/macrophages in the cellular infiltrate, and lower levels of IL-1β, matrix metalloproteinase (MMP)-8 and the chemokine CCL4 compared with confirmed infections (Figure 3b–e, Supplementary Table S3B). Here, CCL4 is linked to infection.